Vehicles operating with combustion cylinders may be configured to inject fuel directly into the fuel chamber. In such a configuration, fuel injected into the cylinder may impinge on the cylinder bore walls and accumulate in the oil pan in the crankcase. If the rate of accumulation exceeds the rate of evaporation of fuel from the crankcase (e.g., via a positive crankcase ventilation (PCV) system), the fuel may dilute oil in the oil pan of the crankcase. Fuel in oil dilution may degrade oil quality, cause fuel odors in the engine oil, and degrade oxygen intake sensors via evaporation.
Other attempts to address fuel in oil dilution include selectively providing coolant to the engine based on fuel in oil dilution. One example approach is shown by Takahashi et al. in U.S. Pat. No. 7,493,883. Therein, a cooling jacket surrounding the crankcase of the engine is included in the coolant circuit when oil in fuel dilution is below a threshold level, and is bypassed in the coolant circuit when oil in fuel dilution is above a threshold level to raise the temperature of the crankcase and provide greater fuel vaporization.
However, the inventors herein have recognized potential issues with such systems. As one example, fuel economy may be degraded in instances where the engine is at a high temperature due to fuel in oil dilution but an acceleration event is commanded. As a further example, coolant may only be fully provided to the engine crankcase or absent from the cooling jacket, and not partially provided to the cooling jacket, providing a less than desired level of temperature control of the engine crankcase.
In one example, the issues described above may be addressed by selectively adjusting a grille shutter opening responsive to fuel in oil dilution. The adjusting of the grille shutter responsive to fuel in oil dilution may be in coordination with adjusting the grille shutter to control coolant temperature and aerodynamics for maintenance of engine cooling performance and improved fuel economy, respectively.
As one example, in response to a fuel in oil dilution level above an upper threshold, a grille shutter may be adjusted from a first mid-point position further from the fully closed position to a second mid-point position closer to the fully closed position. Temperatures within the engine compartment may then increase, and more fuel may vaporize out of the oil in the crankcase. In response to a fuel in oil dilution level returning to below the upper threshold, a grille shutter may be adjusted from the second mid-point position to a different position based on one or more of coolant temperature, charge air cooler temperature, and various vehicle motion parameters. In this way, fuel in oil dilution may be improved while still enabling accurate control of coolant temperature and improving fuel economy.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.